Tracking Cryptosporidium in urban wastewater treatment plants in a cold region: Occurrence, species and infectivity

Dan Xiao, Zhaofeng Lyu, Shiheng Chen, Yang Huo, Wei Fan, Mingxin Huo

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Front. Environ. Sci. Eng. ›› 2022, Vol. 16 ›› Issue (9) : 112. DOI: 10.1007/s11783-022-1533-8
RESEARCH ARTICLE
RESEARCH ARTICLE

Tracking Cryptosporidium in urban wastewater treatment plants in a cold region: Occurrence, species and infectivity

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Highlights

Cryptosporidium in WWTPs in a cold region was investigated in different seasons.

• The overall removal efficiency of Cryptosporidium in WWTPs was over 84%.

• The infectivity rate declined below 53% in effluents mainly due to disinfection.

• The infectivity of Cryptosporidium increased with a seasonal drop in temperature.

• Low temperature promotes binding protein retention and virulence genes expression.

Abstract

This study investigated the occurrence, species, infectivity and removal efficiency of Cryptosporidium spp. across typical wastewater treatment train. Samples from different process units were collected seasonally and synchronously from four wastewater treatment plants (WWTPs) in Northeastern China. Live Cryptosporidium oocysts were identified in most samples from both influent (97.50%) and effluent (90.00%) wastewaters of the four WWTPs, at an average density of 26.34 and 4.15 oocysts/L, respectively. The overall removal efficiency was 84.25%, and oocysts were mainly removed (62.01%) by the modified secondary sedimentation process. Ten Cryptosporidium species were identified in the effluent samples. C. andersoni, C. bovis, and C. ryanae were the three most prevalent species. Oocyst viability assays indicated no reduction of excystation rate during the primary and secondary wastewater treatments (varied in the range of 63.08%–68.50%), but the excystation rate declined to 52.21% in the effluent after disinfection. Notably, the Cryptosporidium oocysts showed higher infection intensity in the cold season (winter and spring) than that in summer and autumn. The influences of environmental temperature on virulence factors of Cryptosporidium were further examined. It was observed that more extracellular secretory proteins were bound on the oocyst surface and several virulence genes were expressed relatively strongly at low temperatures, both of which could facilitate oocyst adhesion, invasion, and host immune evasion. This research is of considerable interest since it serves as an important step towards more accurate panoramic recognition of Cryptosporidium risk reduction in WWTPs, and especially highlights the potential health risk associated with Cryptosporidium in cold regions/seasons.

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Keywords

WWTPs / Cryptosporidium / Occurrence / Species / Infectivity / Low temperature

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Dan Xiao, Zhaofeng Lyu, Shiheng Chen, Yang Huo, Wei Fan, Mingxin Huo. Tracking Cryptosporidium in urban wastewater treatment plants in a cold region: Occurrence, species and infectivity. Front. Environ. Sci. Eng., 2022, 16(9): 112 https://doi.org/10.1007/s11783-022-1533-8

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Acknowledgements

This work was funded by the National Natural Science Foundation of China (Grant Nos. 51908062 and 51978135). It was also supported by the Scientific and Technological Development Plan Project of Jilin Province (China) (No. 20200201042JC). We thank Blessing Ifeoluwa Ogunniran for her linguistic and editing assistance during the revision of this manuscript.

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